1. Field of the Invention
The present invention relates to a method and circuitry for transmission of communication signals in a broad-band communications network.
2. Description of the Prior Art
There is known in the prior art a broad-band communications network (Der Fernmelde-Ingenieur, Vol. 41, Sept., 1987, No. 9, "Exchange Technique in Packet Transmission Systems," pp. 2-8) in which signals of different services according to an ATD (asynchronous time division) method, i.e., are transmitted in packets. The broad-band communications network has packing/depacking devices for forming packets and breaking up packets at the network interfaces.
In broad-band communications networks, wherein packets of a fixed length are transmitted, there is a lag in transmission of communications signals due to the required packing/depacking times as well as the processing and waiting times in the exchange equipment which can has negative effects on the quality of speech signal transmissions. Thus if the lag time is too long, this can result in undesirably long speech pauses which interfere with the speech flow. Furthermore, additional problems can occur in a transfer in broad-band communications networks to which switching networks also belong in addition to packet switching network to which the subscriber units are connected by hybrid sets. Such problems are that the transit times of echo signals caused by the hybrid set assume such an order of magnitude due to the aforementioned lag times in the packet switching network that the echo signals are perceived as interference by the telephone subscribers.
Such echo signals can now be suppressed by means of echo suppressors or echo compensators connected to the transmission lines. However, this requires a certain circuitry expense which is undesirable in some cases. In addition, in order to reduce the lag times in broad-band packet switching networks, there have already been proposals whereby packets of a fixed length are occupied only in part by speech signals in speech signal transmissions.
The problem which the present invention solves is to provide a method and apparatus whereby the lag times due to the packet switching network are reduced in the transmission of communications signals taking place at least partially in a packet switching network.